A blue mason in the lodge

This little bee appeared in my new bee house on 18th May.  It is a female blue mason bee (Osmia caerulescens) and is the first I have seen.  In the photo above it is in a 4mm hole so you can judge its size.  The next photo shows a red mason bee (below) in an 8mm hole and the blue mason (above) in a 4mm hole to give a size comparison.

Unlike red mason bees, which build the cell walls in their nests with mud, the blue mason bee uses chewed up leaves.  This bee sat around for two weeks but eventually started the first cell on 2nd June.

She then did nothing else until 14th June when she eventually restarted work.  You can see that the pollen she was collecting is mostly grey, probably raspberry as the summer-fruiting raspberries were in flower at the time.

I am puzzled by the delay.  Blue mason bees are scarce locally - Steven Falk's book describes it as "rather localised and rarely common anywhere".  I have only ever seen one male before, four years ago - so I wonder if she was having difficulty locating a mate.  Here is the male blue mason bee from four years ago.  He's smaller than the female.

After the slow start this year's female got on with the job.  Two days later her third cell was almost complete.

Here the bee is regurgitating more nectar onto the pollen in the third cell.

Because there is no room to turn round she then has to reverse to the entrance, turn around,

and reverse back in to unload more pollen from the scopa (pollen brush) under her abdomen.

A short while later the next cell wall is almost complete.

And then on to the next one.  By this time she was also collecting pale yellow pollen.  First more nectar,

then turn around again,

more reversing (you can see the pale pollen on her scopa),

and then unloading the pollen with her back legs.

After the delayed start she eventually completed nine cells in nine days.  The nest is sealed with masticated leaves as well.

Like the red mason bees, she left a space at the front with a false wall to discourage predation or parasitisation.

Here is the bee resting on the garage door, her life's work complete.  That is the last I saw of her.

And this is how it looks now, with a red mason nest above.  Each of the nine cells contains a larva, soon to spin a cocoon and metamorphose into a bee.

Then the bees wait until next spring before emerging to start the cycle over again.  I hope I'll be waiting with a camera to see them emerge.

My first observation bee house contained only 8mm holes.  I am very pleased I provided the 4mm and 6mm holes as well in this one.  Other things have also taken advantage of the smaller holes - more news to follow!